Third phase of South Fork Chinook study now afloat
COUGAR RESERVOIR: People coming around the turn at the top of Cougar Dam will be seeing a one-of-a-kind sight for the next two years. Floating at the corner of the reservoir is a $5 million metal fish trap. Dubbed the “Portable Floating Fish Collector,” the structure was created to give researchers a look below the surface so they can study how juvenile salmon interact with the man made structures they encounter during their journey out to the Pacific Ocean.
“The problem is the ‘cul-de-sac’ at the corner of the reservoir where the dam’s temperature control tower is located. Flow conditions there make it hard for fish to find and enter the tower,” according to David Griffith, a fish biologist from the U.S. Army Corps of Engineers Program, Planning and Project Management Division’s environmental group. “We need to know if we can provide better conditions that are conducive to getting the fish to enter the tower.”
“Things are a lot different here than they are on the Columbia,” according to Scott Clemans, a Corps Public Affairs spokesman. “There things have been known for generations. Here we have a completely different set of circumstances.
What fish encounter when they head out to migrate downstream locally is a high head where water levels can fluctuate from 170 to 180 feet.
The Portable Floating Fish Collector is a large pump-driven intake and collection structure surrounded by a floating hull. During a two-year study it will remain moored in a position in front of the temperature control tower (which the fish need to pass through to get downstream). Water will be pumped through the collector at rates ranging from 50 to 100 cubic feet per second, according to Greg Taylor, a Corps fisheries biologist.
Those test began last week. Already, Taylor said, they’ve had some success. “Some of the fish on site that entered the reservoir in the last week or so are two inches long. Fish that have been here for about a year are about six or seven inches.”
The PFFC is equipped with a tag detector and other imaging equipment to help record how efficient the different flows are at collecting fish.
“We want to learn what these juvenile salmon do in the reservoir along with what the conditions are that will attract them into that tower,” he said. “What we’ve discovered is if they’ll go in the tower, they’ll pass through pretty successfully.”
Getting fish to pass through a high head dam will be the third part of a three pronged approach to lessen impacts on their life cycle. Already in place at Cougar is the water temperature control tower and a downstream fish collector that captures adult fish so the can be trucked upstream on their way to spawn.
Those designs have proven their worth locally and have been adopted at other dams. Plans are to take the collector to other locations after the study phase here is complete. To live up to its “portable” designation, that will call for about ten semitrailers and the 360-ton crane that were required to install it.
Image above:Fisheries biologists Greg Taylor, left, and Andrew Janos clear some of the debris away before netting a juvenile that will be part of an ongoing study.
McKenzie River Reflections